[ReaderHighlight] NT: add better support for extending highlights (#13917)

frontend/apps/reader/modules/readerhighlight.lua

@@ -75,6 +75,9 @@ function ReaderHighlight:init()
                 callback = function()
                     this:startSelection(index)
                     this:onClose()
+                    if not Device:isTouchDevice() then
+                        self:onStartHighlightIndicator()
+                    end
                 end,
             }
         end,
@@ -2678,6 +2681,13 @@ function ReaderHighlight:onHighlightPress(skip_tap_check)
         self:onStopHighlightIndicator()
         return true
     end
+    -- Check if we're in select mode (or extending an existing highlight)
+    if self.select_mode and self.highlight_idx then
+        self:onHold(nil, self:_createHighlightGesture("hold"))
+        self:onHoldRelease(nil, self:_createHighlightGesture("hold_release"))
+        self:onStopHighlightIndicator()
+        return true
+    end
     -- Attempt to open an existing highlight
     if not skip_tap_check and self:onTap(nil, self:_createHighlightGesture("tap")) then
         self:onStopHighlightIndicator(true) -- need_clear_selection=true
@@ -2797,6 +2807,16 @@ function ReaderHighlight:onStartHighlightIndicator()
 end
 
 function ReaderHighlight:onStopHighlightIndicator(need_clear_selection)
+    -- If we're in select mode and user presses back, end the selection
+    if self.select_mode and self.highlight_idx then
+        self.select_mode = false
+        if self.ui.annotation.annotations[self.highlight_idx].is_tmp then
+            self:deleteHighlight(self.highlight_idx) -- temporary highlight, delete it
+        else
+            UIManager:setDirty(self.dialog, "ui", self.view.flipping:getRefreshRegion())
+        end
+        self.highlight_idx = nil
+    end
     if self._current_indicator_pos then
         local rect = self._current_indicator_pos
         self._previous_indicator_pos = rect